Peritoneal dialysis is a variant of artificial hemodialysis, where the abdominal membrane (peritoneum) of the patient, which is well supplied with blood, is used as an endogenous filter membrane. Via a catheter, dialysate is introduced into the abdominal cavity. According to the principle of osmosis, urinary constituents are removed from the blood and enter the abdominal cavity. After a few hours, the dialysate with the urinary constituents is discharged from the abdominal cavity.
In principle, different possibilities exist for performing the peritoneal dialysis. In continuous ambulatory peritoneal dialysis (CAPD), the patients themselves replace the dialysate about four to five times a day. In automated peritoneal dialysis (APD), a device, the so-called cycler, performs the automatic bag replacement during the night, so that the patient still is independent during the day.
In automated peritoneal dialysis in which the abdominal cavity is filled by means of the aforementioned cycler, a volume control usually is performed to ensure that no more than a maximum filling volume is administered to the patient. In an average adult, this maximum filling volume for instance is 3500 ml. Usually, standardized values are used for the filling volume, as the effort for an experimental determination of the patient-specific filling volume should be avoided.
In peritoneal dialysis, an access to the abdominal cavity of the patient is provided. Typically, this access is provided by the so-called patient catheter, through which the exchange of fluid is effected. One end of this catheter opens into the abdominal cavity of the patient, and on the other side—outside the patient—a patient connector is provided, which offers a possibility for coupling to a tube system. In the course of time, the catheter can be clogged by deposits, so that its function can be restricted.
To ensure an unrestricted function, the catheter resistance presently is performed manually by the attending physician. A characteristic for the catheter resistance is calculated from the time required for the discharge of a certain volume flow of fluid.